1. Field of the Invention
The present invention relates to a data transfer unit, a data transfer system for transferring data by using a plurality of data transfer units, a data transfer method and a computer-readable recording medium used in the data transfer unit.
2. Description of the Related Art
Conventionally, a data transfer system is known in which a sender transfers data to a plurality of data transfer units directly or via other data transfer units by using another data transfer unit (hereafter referred to as data transfer unit). Such a data transfer system is disclosed, for example, in IETF Internet Draft “draft-ietf-msdp-spec-00”, (Dino Farinacci et al., December 1999).
In the conventional data system, if any fault arises in the course of a data transfer route, a new route is determined between a receiver and the sender in order to avoid loop transfer of the data. Therefore, if any fault has occurred in the course of the data transfer route, there is a problem that the receiver can receive no data until the transfer route is restored.
In conjunction with the above description, a reconfugrable multiple interconnection network with a fault endurance is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-207011). In this reference, a network is composed of a switch node 16 arranged in 2(logbN) stages. The value b is the number of input/output ports of the switch node, and the value N is the number of input/output ports of the network. When an additional stage is added, an additional communication path is provided between the input port and the output port of the network.
Also, a transfer control circuit is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-44658). In this reference, the transfer control circuit actively stores transfers data in a storage section through an asynchronous bus. The transfer control circuit includes an output control circuit which is composed of a hazard-free asynchronous circuit which is composed of one or more function executing circuits, and one or more sequence control circuits. The function execution circuit sends out a control signal to the storage section or the asynchronous bus, and carries out control operation to a writing operation. Also, the function execution circuit outputs a response signal in response to the end of the control operation. The sequence control circuit detects the state of the response signal, selects one or more of the function execution circuits to carry out sequence control to the control operation in a reading operation. Also, the sequence control circuit outputs the response signal in response to the end of the sequence control, such that the condition of the competition to the reading operation can be avoided. One or more of the function execution circuit have delay elements and generates the response signal in response to the end of the control operation in which the time to refer to the storage section is guaranteed. The plurality of sequence control circuits wait for the response signals independent and having different time periods. One or more of the plurality of sequence control circuits detect the states of the response signals, and carry out the sequence control regardless of the state of the response signals generated from the function execution circuits after detecting the end of the operation of the function execution circuits.
Also, a data transfer system between processors is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-77127). In this reference, the system is composed of processors, relaying switches, a cross-bar switch, and a host computer or SVP. Each of the relaying switch and the cross-bar switch is composed of a route instruction circuit, a route data changing circuit, a by-pass instruction circuit and a coincidence determining circuit. For example, when an image is broadcast from a processor PE01, a broadcast message is transferred to a specific one (for example, 135) of the cross-bar switch based on the transfer control data in the message, and route data set for the relaying switch or cross-bar switch. When a fault has occurred in a partial network transferring one-to-one message, the message is transferred to the specific cross-bar switch and transferred from there.
Also, a congestion avoidance system is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 11-177573). In this reference, the system is composed of the following elements. That is, a transmission originator user network transmits transfer packets of an ATM. A destination user network is a destination of the transfer packets from the transmission originator user network. An average inflow speed measurement means measures an average inflow speed of the transfer packets which flows in from the transmission originator user network every destination of the transfer packet from the transmission originator user network. A first congestion detection means detects the first congestion generated when the total amount of the average inflow speed every transmission originator is larger than the transfer rate to the destination user network. A permission inflow speed calculation means calculates permission inflow speed as the average inflow speed of the transfer packets which flow in from the transmission originator user network based on the total amount of the average inflow speeds and the transfer rate. An inflow speed change means sets the average inflow speed of the packets which flows in from the transmission originator user network to a value lower than the permission inflow speed when the first congestion is detected by the first congestion detection means. A relay node relays the transfer packets which are sent and received between the transmission originator user network and the destination user network. An inner node congestion detection means detects inner node congestion generated when the transfer rate of the packets received in the receiving end of this relay node is larger than the transfer rate of the sender of this relay node. A second congestion detection means detects the second congestion generated when the inner node congestion is detected by the node congestion detection means of this inside and moreover the first congestion is not detected by the first congestion detection means. A transfer route database stores the transfer route data corresponding to the transfer from the transmission originator user network to the destination user network and shows a transfer route. A transfer route search means searches a transfer route from this transfer route database while excluding from the transfer route, the relay node in which the inner node congestion is detected by the inner node congestion detection means when second congestion is detected by the second congestion detection means. A transfer route control means carries out the transfer based on the transfer route searched by this transfer route search means.
Also, a data transfer unit is disclosed in Japanese Laid Open Patent Application (JP-A-2000-4247). In this reference, when a change request is generated for a route connection pattern, a CPU 108 selects a proper pattern identifier to avoid a fault by using an in-unit path 107 based on fault data, and rewrites a pattern identifier storage register 105. A route connection data control function section 104 reads out a pattern identifier fro the pattern storage register 105 by using a local bus 106. Next, the route connection data control function section 104 uses the local bus 106 to transfer a route connection data from the pattern storage register group 103 to route connection data storage register groups 171 to 180 in accordance with the pattern identifier. Output side switch contacts 161 to 170 carries out route connection based on data stored in the route connection data storage register groups 171 to 180.